What does a green card holder need to enter Canada and reenter the United States?

When entering from the United States, U.S. citizens are encouraged to show a U.S. passport. If they do not have a passport, they should be prepared to provide photo ID and proof of U.S. citizenship such as a birth certificate, naturalization certificate, or expired U.S. passport. U.S. citizens entering Canada from a third country must have a valid passport. A visa is not required for U.S. citizens for a stay in Canada of up to 180 days. Anyone with a criminal record (including a DWI charge) may be excluded or removed from Canada, and should contact the Canadian Embassy or nearest Canadian consulate before travel. A waiver of exclusion may be available but several weeks? processing are required and a fee must be paid. For further information on entry requirements, travelers may contact the Embassy of Canada at 501 Pennsylvania Avenue, N.W, Washington, D.C. 20001, tel. (202) 682-1740, or the Canadian consulates in Atlanta, Boston, Buffalo, Chicago, Dallas, Detroit, Los Angeles, Miami, Minneapolis, New York, San Juan or Seattle.

2007 UpdateThe Departments of State and Homeland Security require citizens of the United States, Canada, Mexico, and Bermuda to present a passport to enter the United States when arriving by air from any part of the Western Hemisphere as of January 23, 2007.

A separate proposed rule addressing land and sea travel will be published at a later date proposing specific requirements for travelers entering the United States through land and sea border crossings. As early as January 1, 2008, U.S. citizens traveling between the United States and Canada, Mexico, Central and South America, the Caribbean, and Bermuda by land or sea could be required to present a valid U.S. passport or other documents as determined by the Department of Homeland Security.